摘要： http://www.altera.com/literature/hb/max2/max2_mii51009.pdfThe open-drain pin never drives high, only low or tri-state. When the open-drain pinis active, it drives low. When the open-drain pin is inactive, the pin is tri-stated and the trace pulls up to 5.0 V by the external resistor. The purpose of 阅读全文